From Julia Margaret Cameron to Annie Leibovitz, portrait photographers have defined the who’s who of their respective eras — not just by the virtuosity and imagination of their art, but by the very choice of whom to shoot. Mariana Cook has ventured far beyond the more obvious realms of our glutted celebrity culture to get at truths about her time and place — a time that is accelerated, and a place that is globalized. Impelled by her innate curiosity about the creative lives of achievers both renowned and obscure, she has painstakingly assembled series on relationships (couples, fathers and daughters, mothers and sons) and on professions (mathematicians, scientists, artists, human rights activists). Travelling the world at her own expense, and using every sort of entreaty to win their agreement to pose, Cook has captured the countenances of innumerable mid-career and late-career champions in their fields. In some cases, the sessions proved prescient, in both felicitous ways (Barack and Michelle Obama as unknown young Chicago lawyers) and not (Robin Williams alongside his mother).

Cook’s interest in people was ignited early. She was raised by a father who was a psychiatrist, and grew up in New York, the capital of American culture, inhabited by many of the innovators she came to be fascinated by professionally. From her earliest efforts with the Brownie her father gave her, through her darkroom training in a well-equipped high school class, to her photographic studies at Yale, Cook has developed her use of the medium into an agile, instinctive method of fixing fluid personality in revelatory moments. Her images, harvesting natural light and almost exclusively in black and white, are crisp, lucid, and legible — sometimes employing props or found tableaux, but more often refined by a signature velvet black background that amplifies and animates her sitters’ expressions. “Nothing happens in my portraits,” says Cook. “They’re mostly sitting or standing there and you have to read the pictures. They’re deceptively simple, but they’re not so simple.”

Cook’s portraits are usually accompanied by texts distilled from interviews she conducts with her subjects (afterward, she says, because she prefers the shoot itself to remain as meditative as possible). This provides her, and her audience, with a verbal layer of insight not normally accessible to photographers. Each series entails its own investigation into the secrets of creative endeavor and human connection: How does artistic inspiration germinate? How are couples tied together and what keeps their union intact? What makes some people pursue justice against all odds? What is the special rapport distinct to mothers and sons? As with any portrait-maker, the inherent conundrum is just how much of the subject’s interior can be exposed in a single exterior image? To what extent is the complex career (and life) of Jasper Johns, Norman Mailer, Desmond Tutu or Francis Crick revealed in an intimate instant? Faces and gestures safekeep as much as they betray.

But humans are insatiable for likenesses, particularly of those who have climbed great heights of accomplishment and courage. With her own empathic way of seeing the world, Cook gives us a far more generous sampling of these alpha souls than most photographers manage. She’s tireless in corralling her prey but finally philosophical about the results. “If an image is successful it has a life of its own. Time is the true test. They’re like children — you just do the best that you can and then send them out into the world, and they hold their own or they don’t.”

Portrait books by Mariana Cook: Justice: Faces of the Human Rights Revolution (Damiani, 2013), Mathematicians: An Outer View of the Inner World (Princeton University Press, 2009), Faces of Science: Portraits (W.W. Norton, 2005), Couples: Speaking from the Heart (Chronicle Books, 2000), Generations of Women: In Their Own Words (Chronicle Books, 1998), Mothers and Sons: In Their Own Words (Chronicle Books, 1996), Fathers and Daughters: In Their Own Words (Chronicle Books, 1994).